The coupling of a proton gradient across a membrane to energy consumption such as phosphate bond formation is widespread, occurring also in cell development and differentiation, regulation, and motility, photosynthesis, and acidification of the stomach. But the mechanism by which the protons are conducted is only partially understood. Each research group tends to focus on one particular system. As insights are gained in each of these systems, it is important that this information be shared with all those working on the general problem as these insights will undoubtedly prove useful in more than one system. It is for just this purpose of bringing together researchers working on disparate facets of proton transport that the first Gordon Conference on Protons and Membrane Reactions was established in 1985. This meeting traditionally brings together researchers treating a variety of proton-conducting systems using a host of different approaches. One of the strengths of this meeting is the broad range of backgrounds of the scientists which encourages cross-pollination as the sessions address a diverse range of questions. The triannual occurrence of the meeting allows sufficient intervals that the work presented is fresh and interesting. The 1994 Conference will focus on a number of issues beginning with a careful documentation of what is understood about proton transfer in small, well-defined systems. The potential of information from synthetic proton conductors will be discussed, as will recent data dealing with structures of biologically active conductors. Sessions on bacteriorhodopsin and photosynthetic reaction centers will center about recent knowledge about the paths of the protons through the proteins. Another session will be devoted to the various ways in which water molecules can be directly involved in the conduction process and another on proton motion along boundary regions. Protons will be contrasted with other cations in Session 8, followed by recent developments in oxidative phosphorylation.